Medical devices can be used in a body opening, cavity, or tract to manipulate material within the body. Such medical devices may be used through an endoscope or a laparoscope. When inserted into a flexible endoscope, medical devices impair the ability of the flexible endoscope to achieve the desired flexion needed to engage material at a remote body site.
One such medical device has a sheath and an object-engaging unit, such as a basket, that is moveable relative to the sheath from a collapsed state within the sheath to another state in which the unit extends past the distal end of the sheath. Typically, the object-engaging unit is in an operational mode when the object-engaging unit is extended beyond the distal end of the sheath. The sheath typically extends from a handle, located at the proximal end (i.e., the end away from the patient) of the sheath, to the object-engaging unit, which is located at the distal end of the sheath (i.e., the end near the patient and that goes into the patient).
One purpose of the sheath is to collapse and release the object-engaging unit by sliding the sheath over (to collapse) or away from (to release) the object-engaging unit, or by moving the object-engaging unit into (to collapse) and out of (to release) the sheath. The object-engaging unit is, for example, a grasping forcep-like assembly, a basket assembly, or any type of tissue and/or object manipulating, capturing, and/or retrieving assembly. When the object-engaging unit is enclosed within the sheath, the object-engaging unit is inoperative and in its collapsed or withdrawn state. For example, object-engaging units, such as baskets, assume a collapsed, reduced diameter profile when the basket is enclosed within the distal end of the sheath. When the sheath is retracted relative to the basket or the basket is extended beyond the distal end of the sheath, the basket expands to a relatively larger diameter than when the basket is enclosed and collapsed within the sheath. In the expanded position, the basket is positioned and is operable at least to capture material in the body, such as kidney stones. If the object-engaging unit is, for example, a blade, it would be withdrawn when not needed to cut, and then extended at least partially out beyond the distal end of the sheath to allow cutting with the blade. The sheath also serves other purposes. For example, the sheath serves to encompass and protect the object-engaging unit as it is inserted into the body cavity or channel of an endoscope. The sheath also serves to protect the body cavity from damage that may be introduced by the object-engaging unit itself if it were released, expanded, or extended during passage of the sheath into the body. Also, the sheath must provide sufficient strength and rigidity to allow its insertion into the body or endoscope channel while also providing sufficient flexibility to permit the sheath to navigate through the tortuous channels of the body cavity, opening, or tract.